This invention relates to the field of dentistry and more particularly to a method for providing a thin adherent substantially continuous metallic layer over an osseous substrate. In particular, this invention relates to a method for providing a metallic layer over a tooth surface which may serve as a substrate for the subsequent application of an amalgam or other metal filling.
In the practice of dentistry, the restoration of a locally decayed tooth is commonly accomplished by excavating the tooth to remove the decayed portion and filling the excavation with an amalgam. Although this procedure is satisfactory in many respects, its effectiveness for preserving the tooth is limited due to the low level of adherence which exists between the amalgam and the tooth structure at the surface of the excavation. Except for weak van der Waals forces, there is essentially no chemical adhesion between amalgam and an osseous substrate such as tooth structure.
As a consequence of the poor adhesion between amalgam and the tooth, it is generally necessary to drill an excavation in the tooth larger than that required simply to remove the portion of the tooth affected with caries. Undercut recesses are provided within the excavation for mechanical attachment of the amalgam filling to the tooth. The filling is then keyed into these undercut portions so that tooth and filling are mechanically locked together. This procedure adversely affects long term preservation of the tooth because of the relatively large portion of the tooth which must be removed as compared to the size of the portion affected by caries. Moreover, the restoration itself not only fails to positively prevent further decay of the tooth but may actually promote such decay due to secondary caries arising from the percolation of oral fluids through a narrow gap which may exist between the filling and the surface of the excavation. Such a gap may exist because of the lack of adherence between the filling amalgam and the tooth structure, and the resultant percolation of oral fluids may cause secondary caries at the surface of the excavation under the filling.
A need has existed in the art, therefore, for an improved dental restorative technique which provides strong adherence between an amalgam or other type of filling and a tooth excavation so that a filling may be securely applied without the necessity of the relatively large excavations required for mechanical attachment of the filling to the tooth. A need has further existed for such a technique which may eliminate gaps between the surface of the filling and the surface of the excavation through which oral fluids may percolate. In the literature, suggestions have been made to accomplish these results by electroplating. See, for example, Franklin, "Electrodeposition in Dentistry", Plating, Vol. 58, No. 8, August, 1971. However, such general suggestions have apparently not been reduced to a practical method useful in the restoration of teeth.